1. Field of the Invention
The present invention relates to a control system and a control method of a time sharing switch in an electronic switching system, and more particularly, to a time division multiplex highway switch control system and control method of T-S-T three-stage switches in a multiprocessor typed electronic switching system.
2. Description of the Related Art
Generally, there has been used a conventional method of providing a multiprocessor typed electronic switching system with each processor for every predetermined number of accommodating terminals, for the purpose of dispersing the load. When forming a switch of a large volume by use of such a multiprocessor typed electronic switching system, there has been adopted a method of forming a general time sharing switch having a T-S-T three-stage structure, with a plurality of dispersedly provided first T-stages and third T-stages respectively controlled by a plurality of corresponding processors dispersedly provided and with second S-stages centrally controlled by a single processor.
This kind of electronic switching system is disclosed in, for example, Japanese Patent Publication Laid-Open (Kokai) No. Showa 61-58397, xe2x80x9cTime Sharing Communication Channel Control Devicexe2x80x9d. The structure of the conventional general time sharing switch disclosed in the same publication is shown in FIG. 10.
With reference to FIG. 10, the conventional T-S-T three-stage time sharing switch system comprises first switches 11, 12 to 1n, second switches 21, 22 to 2n, third switches 31, 32 to 3n, processors 41, 42 to 4n for controlling the first switches and the third switches, a processor 40 for controlling the second switches 21, 22 to 2n, an interposing bus 60 between processors for connecting the processors 40, 41, 42 to 4n with each other, output highways 71, 72 to 7n for connecting the respective first switches 11, 12 to 1n with all the second switches 21, 22 to 2n, output highways 81, 82 to 8n for connecting the respective second switches 21, 22 to 2n with the corresponding third switches 31, 32 to 3n and a memory 90 storing the spare time slot information of the respective second switches 21, 22 to 2n which are referred to by the processor 40 in order to control the second switches 21, 22 to 2n. 
Considering the case of achieving a switching connection from a terminal 102 under the control of the processor 42 to a terminal 101 under the control of the processor 41, it is necessary to connect a path passing from the terminal 102 to the terminal 101 via the first switch 12, the second switch 21, and the third switch 31, in this connection. In order to enable the second switch to exchange output highways, it is necessary to coincide the time slots on the output side of the first switch and the time slots on the input side of the third switch.
Therefore, the processor 42 on the input side of this connection asks the processor 40 about the spare time slots available for the connection to the third switch 31 accommodating the terminal 101 of the connection party, through the interposing bus 60 between processors. The processor 40 makes a comparison between the spare time slots of the output highway 72 of the first switch 12 used for the connection and the spare time slots of the output highway 81 of the second switch 12, and selects each time slot of being both empty, thereby performing the connection of the corresponding highway. The processor 40 notifies the processor 42 of the selected time slot number xe2x80x9cmxe2x80x9d. The processor 42 interconnects the time slots for accommodating the terminal 101 and the time slots xe2x80x9cmxe2x80x9d in the first switch 12. The processor 42 asks the processor 41 to connect to terminal 101 by use of the time slots xe2x80x9cmxe2x80x9d through the interposing bus 60 between processors. The processor 41 interconnects the time slots for accommodating the terminal 102 and the time slots xe2x80x9cmxe2x80x9d, in the third switch 31. As a result, the connection from the terminal 101 to the terminal 102 is completed.
However, in the above-mentioned conventional highway switch control method, a single processor controls highways. Therefore, when a fault occurs in this processor, the whole system fails to do switching, even if there is no fault in a processor controlling T-stage.
In the above publication, disclosed is an electronic switching system of a redundant structure including a plurality of dispersedly provided time sharing switches and thereby capable of eliminating the fault affecting the whole electronic switching system even if a fault occurs in a common control portion. However, since the ratio of the redundant structure portion in the electronic switching system is increased, this invention is not suitable for a large scaled switching system such as the T-S-T structure.
An object of the present invention is, in order to solve the above problems, to provide an extremely reliable highway switch control system and control method suitable for decentralized control, with commonly controlled portion eliminated from the T-S-T three-stage time sharing switch system.
Another object of the present invention is, in addition to the above object, to provide a highway switch control system and control method suitable for a large-scaled switching structure like a T-S-T structure without redundant circuitry.
According to the first aspect of the invention, a highway switch control system for controlling a time division multiplex highway switch of T-S-T three-stage switches in a multiprocessor typed electronic switching system, comprises
a plurality of sets of first switches of time sharing switching method, second switches of highway switching method, third switches of time sharing switching method, and control means for controlling each switch,
interconnecting means for interconnecting the control means each other in each set,
first output highways for connecting each of the first switches in every set to all the second switches of all sets, and
second output highways for respectively connecting the second switches to the third switches in every set,
two of the control means to be connected together getting information on spare time slots of the mutual switches through the interconnecting means and deciding time slots for use in the connection, thereby controlling a connection between required switches.
In the preferred construction, the highway control system further comprises connection means for exclusive use in connecting the control means to the second switches in each set.
In the preferred construction, the respective sets further comprise storing means for storing information on spare time slots in the respective switches, and the control means decide time slots for use in a connection with reference to the information stored in the storing means.
In another preferred construction, the respective sets further comprise storing means for storing information on spare time slots in the respective switches, and the control means makes a comparison between the information stored in the storing means of one""s own and the information stored in the storing means of the connected party, so to detect the coincident spare time slots, which are defined as the time slots for use in the connection.
According to the second aspect of the invention, a highway switch control method for controlling a time division multiplex highway switch by control means provided correspondingly to first switches of time sharing switching method, second switches of highway switching method, and third switches of time sharing switching method forming T-S-T three-stage switches, in a multiprocessor types electronic switching system, the method comprising the steps of
a step of deciding time slots for use in this connection by examining spare time slots of the first switch and the third switch, when connection the first switch to the third switch, and
a step of connecting an output highway between the first switch and the second switch corresponding to the third switch and an output highway between the second switch and the corresponding third switch, at a timing of the decided time slots for use in the connection.
In the preferred construction, the time slot deciding step further includes a step of delivering an information on the spare time slots of the first switch to the control means controlling the third switch, a step of, upon receipt of the information on the spare time slots of the first switch, deciding the coincident spare time slots as the time slots for use in the connection by making a comparison between the received information and the information on the spare time slots of the third switch, and a step of notifying the control means controlling the first switch of the decided time slots for use in the connection.
According to another aspect of the invention, a computer readable memory storing a computer program for controlling a time division multiplex highway switch by activating control means provided correspondingly to first switches of time sharing switching method, second switches of highway switching method, and third switches of time sharing switching method forming T-S-T three-stage switches, in a multiprocessor typed electronic switching system, the computer program comprising
a step of deciding time slots for use in this connection by examining spare time slots of the first switch and the third switch, when connection the first switch to the third switch, and
a step of connecting an output highway between the first switch and the second switch corresponding to the third switch and an output highway between the second switch and the corresponding third switch, at a timing of the decided time slots for use in the connection.
Other objects, features and advantages of the present invention will become clear from the detailed description given herebelow.